Summary: Discriminating males alter sperm production
between species
Andrea S. Aspbury* and Caitlin R. Gabor
Department of Biology, Texas State University, San Marcos, TX 78666-4615
Edited by David B. Wake, University of California, Berkeley, CA, and approved October 2, 2004 (received for review August 3, 2004)
Prezygotic reproductive isolation and its importance in speciation
is traditionally approached from the viewpoint of those events
that occur before mating. However, recent interest in sperm
competition theory has shown that prezygotic isolation can be
affected by mechanisms that occur after mating but before fertil-
ization. One neglected aspect of these studies is how the cost of
sperm production might play a role in species isolation. We exam-
ined differential sperm production in a species whose males are
sexually parasitized by a unisexual gynogenetic species. Gynogens
are clonal females that require sperm from males of closely related
bisexual species to initiate embryogenesis. We tested for differ-
ential sperm production by male sailfin mollies (Poecilia latipinna)
when they were in the presence of either a heterospecific, gyno-
genetic female (Poecilia formosa, Amazon molly) or a conspecific
female. We found that previously demonstrated male mate choice